/* SPDX-License-Identifier: Apache-2.0 */

/* Copyright 2025 Thorsten Töpper
 *
 * Compare two files with a single SHA1 hash per line
 * useful when comparing filesystem content:
 * find fs_to_check -type f -exec sha1sum "{}" \; > output_1.txt
 * awk ...
 *
 * vim:ts=4:sw=4:expandtab
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdbool.h>
#include <stdint.h>
#include <errno.h>
#include <ctype.h>
#include <inttypes.h>

#include "output.h"
#include "hex_conversion.h"


#ifndef LINELENGTH
#define LINELENGTH 1024
#endif

/* 8 bytes pointer to a smaller char array? As there are strict conditions in
 * regards to the data which will be processed work with fix size arrays and
 * do math hard coded at compile time. */
#define NON_CONVERTED_SIZE      40
#define FULL_DATABLOCK_SIZE     (NON_CONVERTED_SIZE/2)


struct data_field {
    unsigned char data[FULL_DATABLOCK_SIZE]; /* keep this as first element for bsearch */
    bool active;
};

struct list_node {
    struct list_node *next;
    struct data_field *field;
};

struct list_head {
    struct list_node *first_node;
    struct list_node *last_node;
    size_t size;
};

struct list_collection {
    struct list_head *heads[256];
};


struct data_array {
    struct data_field **field;
    size_t entry_points[256]; /* keep constant */
    size_t opt_entry_points[256]; /* increase if referred target is deactivated */
    size_t array_length;
};


void apply_filter_to_array(struct data_array *array, unsigned char *data);
int compare_data_fields(const void *a, const void *b);
struct data_array *convert_collection_to_array(struct list_collection *collection);
struct list_collection *create_collection();
struct list_head *create_list_head();
struct list_node *create_list_node(unsigned char *data);
void destroy_collection(struct list_collection *c);
void destroy_data_array(struct data_array *da);
void destroy_list(struct list_head *head);
void fprint_array(FILE *fd, struct data_array *da);
struct list_collection *import_file_into_collection(char *filename);
bool insert_into_sorted_collection(struct list_collection *collection, unsigned char *data);
bool run_filter_file_on_array(struct data_array *da, char *filename);
bool search_data_in_array(struct data_array *da, unsigned char *data);
bool verify_data_array(struct data_array *da);
bool verify_list_collection(struct list_collection *lc);

#ifdef DEBUGBUILD
void print_collection_state(struct list_collection *coll);
#endif


/* === IMPLEMENTATION === */

inline struct list_collection *create_collection() {
    int i;
    struct list_collection *c;

    if ((c=calloc(1, sizeof(struct list_collection))) == NULL) {
        return NULL;
    }
    for (i=0; i<256; i++) {
        c->heads[i] = create_list_head();
        if (c->heads[i] == NULL) { break; }
    }
    DBGTRC("DEBUG: %d lists initialized%s\n", i,
            (i<256)?", aborting as not all 256 where" : "");
    return c;
}


inline struct list_head *create_list_head() {
    struct list_head *head = calloc(1, sizeof(struct list_head));
    if (head == NULL) {
        /* If the following masked fprintf calls fail there was a chance */
        LOGERR("ERROR: Failed to allocate memory for list_head: ");
        fputs(strerror(errno), stderr);
        fputc('\n', stderr);
        return NULL;
    }
    head->first_node = NULL;
    head->last_node = NULL;
    head->size = 0;
    return head;
}

/* bsearch and similar  */
int compare_data_fields(const void *a, const void *b) {
    return memcmp(((struct data_field*)a)->data,
            ((struct data_field*)b)->data, FULL_DATABLOCK_SIZE);
}


inline bool search_data_in_array(struct data_array *array, unsigned char *data) {
    struct data_field *df, tmp_df;
    memcpy(tmp_df.data, data, FULL_DATABLOCK_SIZE);
    /* Currently not working */
    df = bsearch(&tmp_df, array->field,
            array->array_length, sizeof(struct data_field),
            compare_data_fields);
    if (df != NULL) {
        return true;
    }
    return false;
}


inline void destroy_collection(struct list_collection *c) {
    int i;
    if (c == NULL) return;
    for (i=0; i<256; i++) {
        destroy_list(c->heads[i]);
    }
    free(c);
}


inline void destroy_list(struct list_head *head) {
    struct list_node *ptr=NULL;
    if (head == NULL) return;
    while (head->first_node !=  NULL) {
        ptr = head->first_node;
        head->first_node = head->first_node->next;
        if (ptr->field != NULL)
            free(ptr->field);
        free(ptr);
    }
    free(head);
    head = NULL;
}

inline void destroy_data_array(struct data_array *da) {
    size_t i=0;
    if (da == NULL) return;
    for (;i<da->array_length; i++) {
        if (da->field[i] != NULL) {
            free(da->field[i]);
        }
    }
    free(da->field);
    free(da);
}

inline struct list_node *create_list_node(unsigned char *data) {
    struct list_node *node;
    if (data == NULL) return NULL;
    if ((node=calloc(1,sizeof(struct list_node))) == NULL) {
        LOGERR("ERROR: Failed to allocate a few bytes for new list_node\n");
        return NULL;
    }
    if ((node->field=calloc(1,sizeof(struct data_field))) == NULL) {
        LOGERR("ERROR: Failed to allocate a few bytes for new data_field\n");
        free(node);
        return NULL;
    }
    node->next = NULL;
    node->field->active = true;
    memcpy(node->field->data, data, FULL_DATABLOCK_SIZE);
    return node;
}


/* If the input data's already sorted best performance, worst case (O^n)/256 if it's reverse sorted. */
inline bool insert_into_sorted_collection(struct list_collection *collection, unsigned char *data) {
    struct list_node *node_ptr = NULL, *tmp_node = NULL;
    struct list_head *head_ptr = NULL;
    int cmp = 0;
#ifdef DEBUGBUILD
    static size_t fcall_count = 0;
#endif

    if (collection == NULL || data == NULL) {
        DBGTRC("ERROR: collection set%s / data set%s\n",
                ((collection==NULL) ? " NULL" : ""),
                ((data==NULL)       ? " NULL" : ""));
        return false;
    }

#ifdef DEBUGBUILD
    DBGTRC("DEBUG: fcall_count = %lu / data[0]=0x%02X / decimal: data[0]=%3u\n",
            ++fcall_count, data[0], (unsigned int)data[0]);
#endif

    head_ptr = collection->heads[data[0]];
    if (head_ptr->first_node == NULL) {
        DBGTRC("DEBUG: First node for list %d\n", data[0]);
        if ((tmp_node = create_list_node(data)) == NULL) {
            return false;
        }
        head_ptr->first_node = tmp_node;
        head_ptr->last_node = tmp_node;
        head_ptr->size = 1;
        return true;
    }

    cmp = memcmp(data, head_ptr->last_node->field->data, FULL_DATABLOCK_SIZE);
    if (cmp == 0) {
        /* duplicate, skip */
        return true;
    }

    /* Append to list */
    if (cmp > 0) {
        if ((tmp_node = create_list_node(data)) == NULL) {
            return false;
        }
        head_ptr->last_node->next = tmp_node;
        head_ptr->last_node = tmp_node;
        head_ptr->size++;
        return true;
    }

    node_ptr = head_ptr->first_node;
    cmp = memcmp(data, node_ptr->field->data, FULL_DATABLOCK_SIZE);
    if (cmp == 0) { return true; }
    /* First to enter? Prepend to list*/
    if (cmp < 0) {
        if ((tmp_node = create_list_node(data)) == NULL) {
            return false;
        }
        tmp_node->next = head_ptr->first_node;
        head_ptr->first_node = tmp_node;
        head_ptr->size++;
        return true;
    }

    /* Sloooow part... */
    while (node_ptr->next != NULL) {
        /* check next in list */
        cmp = memcmp(data, node_ptr->next->field->data, FULL_DATABLOCK_SIZE);
        if (cmp == 0) { return true; }
        /* insert by prepend */
        if (cmp > 0) {
            if ((tmp_node = create_list_node(data)) == NULL) {
                return false;
            }
            tmp_node->next = node_ptr->next;
            node_ptr->next = tmp_node;
            head_ptr->size++;
            return true;
        }
        /* continue */
        node_ptr = node_ptr->next;
    }
    LOGERR("ERROR: Could not insert dataset into list, missed possible situation...\n");
    return false;
}


inline struct data_array *convert_collection_to_array(struct list_collection *collection) {
    int i;
    size_t s;
    struct data_array *da = NULL;
    struct list_node *ptr, *tmp;

    if (collection == NULL) {
        LOGERR("ERROR: No collection given.\n");
        return NULL;
    }

    s = 0;
    for (i=0; i<256; i++) {
#ifdef DEBUGBUILD
        if (collection->heads[i]->size > 0) {
            DBGTRC("DEBUG: collections->heads[%d]->size = %lu\n",
                i, collection->heads[i]->size);
        }
#endif
        s += collection->heads[i]->size;
        DBGTRC("DEBUG: collection->heads[%d]->size = %lu\n", i, collection->heads[i]->size);
    }
    DBGTRC("DEBUG: Total size %lu\n", s);

    if (s == 0) {
        LOGERR("ERROR: Empty collection.");
        return NULL;
    }

    if ((da = calloc(1, sizeof(struct data_array))) == NULL) {
        LOGERR("ERROR: Failed to allocate %lu bytes...\n", sizeof(struct data_array));
        return NULL;
    }

    da->array_length = s;
    if ((da->field=calloc(da->array_length, sizeof(struct data_field*))) == NULL) {
        free(da);
        LOGERR("ERROR: Failed to allocate memory for metadata\n");
        return NULL;
    }

    s = 0;
    for (i=0; i<256; i++) {
        DBGTRC("DEBUG: i=%d / s=%lu\n", i, s);
        ptr = collection->heads[i]->first_node;
        da->entry_points[i] = s;
        da->opt_entry_points[i] = s;
#ifdef DEBUGBUILD
        if (ptr != NULL) {
            DBGTRC("DEBUG: list %d in collection, claims size %lu\n", i,
                    collection->heads[i]->size);
        }
#endif
        while (ptr != NULL) {
            DBGTRC("DEBUG: Setting field %lu to %s\n", s,
                    (ptr->field == NULL) ? "NULL" : "valid value");
            da->field[s] = ptr->field;
            s += 1; /* field[s++] failed... compiler optimization? */
            tmp = ptr->next;
            ptr->next = NULL;
            free(ptr);
            ptr = tmp;
        }
        collection->heads[i]->first_node = NULL;
        collection->heads[i]->last_node = NULL;
        collection->heads[i]->size = 0;
    }

    destroy_collection(collection);

    return da;
}


/* This is acceptable if the largest can be hold in memory, but not the other way */
inline void apply_filter_to_array(struct data_array *array, unsigned char *data) {
    size_t pos=0, limit = 0;
    int cmp;


    if (array==NULL || data==NULL) {
        return;
    }

    /* Manual search with entry_points */
    if (data[0] == 255) {
        limit = array->array_length;
    } else {
        limit = array->entry_points[data[0]+1];
    }

    pos=array->opt_entry_points[data[0]];
    DBGTRC("DEBUG: opt_entry_point=%-8lu / limit=%-8lu\n", pos, limit);
    DBGTRC("DEBUG: data[0]=0x%02X / decimal: data[0]=%3u\n",
            data[0], (unsigned int)data[0]);
    /* TODO: Evaluate whether this loop should be handlued with openmp */
    for (; pos<limit; pos++) {
        DBGTRC("DEBUG: pos=%lu\n", pos);
        if (array->field[pos]->active) {
            /* perf optimization, single byte faster than memcmp on 20 bytes */
            if (data[1] < array->field[pos]->data[1]) {
                continue;
            }
            cmp = memcmp(data, array->field[pos]->data, FULL_DATABLOCK_SIZE);
            DBGTRC("cmp: %d\n", cmp);
            if (cmp == 0) {
                array->field[pos]->active = false;
                if (pos == array->opt_entry_points[data[0]]) {
                    array->opt_entry_points[data[0]]++;
                }
                return;
            }
#if 1
            else if (data[1] > array->field[pos]->data[1]) {
                return;
            }
#else
            /* Currently I don't trust this memcmp result 100%. testdata created in shell
             * for i in $(seq 1 20000); do echo "foo_$i" | sha1sum | awk ' { print $1; } ' ; done
             * picking a random subset from there to be used as filters lead to sometimes leaving
             * the loop too early with this else... Comparing only the second byte may is also too
             * vague with really large datasets */
            else if (cmp < 0) {
                /* array content is sorted, so abort once the possible match has been passed */
                return;
            }
#endif
        }
    }
}


struct list_collection *import_file_into_collection(char *filename) {
    FILE *fd = NULL;
    char line[LINELENGTH];
    unsigned char data[FULL_DATABLOCK_SIZE];
    size_t line_nr = 0;
    struct list_collection *collection = NULL;

    if (filename == NULL || filename[0] == '\0') {
        LOGERR("ERROR: no filename given.\n");
        return NULL;
    }

    if ((collection = create_collection()) == NULL) {
        LOGERR("ERROR: Failed to allocate a few bytes for collection.\n");
        return NULL;
    }

    if ((fd = fopen(filename, "r")) == NULL) {
        LOGERR("ERROR: Failed to open file '%s': %s (errno %d)\n",
                filename, strerror(errno), errno);
        destroy_collection(collection);
        return NULL;
    }

    while (fgets(line, LINELENGTH, fd) != NULL) {
        line_nr++;
        DBGTRC("DEBUG: line %lu = %s", line_nr, line);
        if (convert_line(line)<0) {
            LOGERR("ERROR: Failed to prepare line %lu for conversion.\n", line_nr);
            destroy_collection(collection);
            fclose(fd);
            return NULL;
        }

        if (convert_to_binary(line, data) == NULL) {
            destroy_collection(collection);
            fclose(fd);
            LOGERR("ERROR: Failed to convert line %lu into binary data.\n", line_nr);
            return NULL;
        }

        if (!insert_into_sorted_collection(collection, data)) {
            destroy_collection(collection);
            fclose(fd);
            LOGERR("ERROR: Failed to insert line %lu in binary form into collection.\n", line_nr);
            return NULL;
        }
    }

    DBGTRC("DEBUG: lines read %lu\n", line_nr);
    fclose(fd);

    return collection;
}


bool run_filter_file_on_array(struct data_array *da, char *filename) {
    FILE *fd = NULL;
    size_t line_nr = 0;
    char line[LINELENGTH];
    unsigned char data[FULL_DATABLOCK_SIZE];

    if (da == NULL || filename == NULL || filename[0] == '\0') {
        LOGERR("ERROR: compromised arguments at call.\n");
        return false;
    }
    if ((fd=fopen(filename, "r")) == NULL) {
        LOGERR("ERROR: Failed to open file '%s': %s (errno %d)\n",
                filename, strerror(errno), errno);
        return false;
    }

    /* Be nice and skip and not abort */
    while (fgets(line, LINELENGTH, fd) != NULL) {
        line_nr++;
        DBGTRC("READ LINE %lu: %s", line_nr, line);
        if (convert_line(line)<0) {
            LOGERR("ERROR: Failed to prepare line %lu for conversion.\n", line_nr);
            continue;
        }
        if (convert_to_binary(line, data) == NULL) {
            LOGERR("ERROR: Failed to convert line %lu into binary data.\n", line_nr);
            continue;
        }
        apply_filter_to_array(da, (unsigned char*)data);
    }

    fclose(fd);

    return true;
}


void fprint_array(FILE *fd, struct data_array *da) {
    FILE *fdout = stdout;
    char *plaintext = NULL;
    size_t pos;
    if (da == NULL) { return; }
    if (fd != NULL) { fdout = fd; }
    DBGTRC("DEBUG: da->array_length = %lu\n", da->array_length);
    for (pos=0; pos < da->array_length; pos++) {
        DBGTRC("DEBUG: pos %lu --- %s\n", pos, (da->field[pos] == NULL)? "NULL" : "element exists");
        if (da->field[pos]->active) {
            plaintext = convert_from_binary(da->field[pos]->data, FULL_DATABLOCK_SIZE, plaintext);
            fputs(plaintext, fdout);
            fputc('\n', fdout);
        }
    }
    if (plaintext != NULL) { free(plaintext); };
}

/* To be used on a new array */
bool verify_data_array(struct data_array *da) {
    bool res = true;
    size_t p = 0;
    int repeated_error = 0;

    if (da == NULL) {
        LOGERR("No array given...\n");
        return false;
    }

    /* Check entry points */
    for (p=0; p<256; p++) {
        if (da->entry_points[p] != da->opt_entry_points[p]) {
            LOGERR("MISMATCH entry_points[%lu] <-> opt_entry_points[%lu]\n", p, p);
            res = false;
        }
    }

    for (p=0; p<da->array_length; p++) {
        if (da->field[p] == NULL) {
            LOGERR("ERROR: field %lu of %lu is NULL.\n", p, da->array_length);
            res = false;
            repeated_error++;
            if (repeated_error > 5)
                return res;
        }
    }

    return res;
}


bool verify_list_collection(struct list_collection *lc) {
    bool res = true;
    int i;
    size_t count;
    struct list_node *ptr;

    for (i=0; i<256; i++) {
        count = 0;
        ptr = lc->heads[i]->first_node;

        while (ptr != NULL) {
            count++;
            ptr = ptr->next;
        }

        LOGERR("DEBUG: list %3d/0x%02X: size %lu, counted %lu => does%s match.\n",
                i, i, lc->heads[i]->size, count,
                (lc->heads[i]->size != count)?" NOT":"");
        if (lc->heads[i]->size != count) {
            res = false;
        }
    }

    return res;
}


#ifdef DEBUGBUILD
void print_collection_state(struct list_collection *coll) {
    int i = 0;
    struct list_head *h = NULL;
    struct list_node *ptr = NULL;

    if (coll == NULL) {
        LOGERR("ERROR: No collection given\n");
        return;
    }

    for (i=0; i<256; i++) {
        h = coll->heads[i];
        ptr = h->first_node;
        if (h->size == 0 || ptr == NULL) {
            if (!(h->size == 0 && ptr == NULL)) {
                DBGTRC("DEBUG: ERROR item %3d not matching size %lu, first_node %p\n", i, h->size, h->first_node);
            }
            continue;
        }
        DBGTRC("DEBUG: List %3d, size %lu, first_node %p\n", i, h->size, h->first_node);
    }

}
#endif

int main(int argc, char **argv) {
    FILE *output = NULL;
    int i = 0;
    size_t s = 0;
    struct list_collection *collection;
    struct data_array *array;

    if (argc < 3) {
        fprintf(stderr, "Usage: %s output raw_data filter_files...\n", argv[0]);
        return EXIT_FAILURE;
    }

    s = strlen(argv[1]);
    if (s == 6 && (strncmp("stdout", argv[1], 6) == 0)) {
        output = stdout;
    } else {
        if ((output=fopen(argv[1], "w")) == NULL) {
            LOGERR("ERROR: Failed to open file '%s': %s (errno %d)\n",
                    argv[1], strerror(errno), errno);
            return EXIT_FAILURE;
        }
    }

    LOGERR("IMPORT FILE %s\n", argv[2]);
    collection = import_file_into_collection(argv[2]);
    if (collection == NULL) {
        return EXIT_FAILURE;
    }
/* TODO: Hide this behind some option
    if ( ! verify_list_collection(collection) ) {
        return EXIT_FAILURE;
    }
*/
    array = convert_collection_to_array(collection);
    if (array == NULL) {
        return EXIT_FAILURE;
    }
    collection = NULL;

/* TODO: Hide this behind an option
    if ( ! verify_data_array(array) ) {
        return EXIT_FAILURE;
    }
*/

    for (i=3; i<argc; i++) {
        LOGERR("APPLY FILTER FILE %s\n", argv[i]);
        if (!run_filter_file_on_array(array, argv[i])) {
            LOGERR("ERROR: Aborting.\n");
            return EXIT_FAILURE;
        }
    }
    DBGTRC("DEBUG: Filter applied, final result:\n");
    fprint_array(output, array);
    fflush(output);
    fclose(output);

    destroy_data_array(array);

    return EXIT_SUCCESS;
}